Reverse String and Binary Search of floating point values, C#

Reverse String and Binary Search of floating point values

//Tableau Interview Homework
//Rextester.Program.Main is the entry point for your code. Don't change it.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            
            Console.WriteLine("Thanks for the opportunity!");
            Console.WriteLine();
            
            Console.WriteLine("Reverse string - tests:");
            Console.WriteLine("~~~~~~~~~~~~~~~~~~~~~~~");
            Console.WriteLine("Time complexity: O(n/2) and Space complexity: O(n), where n is the number of characters in the string. Space complexity would be O(1) if the input is given as a char[].");
            Console.WriteLine();
            Assert("I am sam." == ReverseString(".mas ma I"), "reverses a small sentence");
            Assert("ab" == ReverseString("ba"), "reverses a 2 letter string");
            Assert("a" == ReverseString("a"), "reverses a 1 letter string");
            Assert(string.Empty == ReverseString(null), "returns string.Empty for null");
            Assert(string.Empty == ReverseString(string.Empty), "returns string.Empty for string.Empty");
            Assert("அஆஇஈஉ" == ReverseString("உஈஇஆஅ"), "handles unicode characters");
            
            Console.WriteLine();
            
            Console.WriteLine("Binary search of floating point values - tests:");
            Console.WriteLine("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
            Console.WriteLine("Time complexity: O(log n) and Space complexity: O(1), where n is the number of elements in the input array.");
            Console.WriteLine();
            double[] input = new double[] {-0.989, -0.989999, -0.990001, 0.999999, 1.0};
            Array.Sort(input); //sort to save yourself from the test being wrong
            Assert(2 == FindClosestMatchIndex(input, -0.990001), "finds the straight match");
            Assert(1 == FindClosestMatchIndex(input, -0.989989), "finds when greater is the closest");
            Assert(3 == FindClosestMatchIndex(input, 0.9999991),"finds when lower is the closest");
            Assert(0 == FindClosestMatchIndex(input, -9999999),"finds when the first is the closest by being greater");
            Assert(0 == FindClosestMatchIndex(input, -0.991),"finds when the first is the closest by being lesser");
            Assert(4 == FindClosestMatchIndex(input, 0.9999999),"finds when the last is the closest by being greater");
            Assert(4 == FindClosestMatchIndex(input, 99999999),"find swhen the last is the closest by being lesser");
            Assert(-1 == FindClosestMatchIndex(new double[0], 99999999),"returns -1 when the array is empty");
            
            Console.WriteLine();
            
            Console.WriteLine("Binary search of LARGE, PRECISE, DUPLICATE floating point values - tests:");
            Console.WriteLine("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
            Console.WriteLine();
            double[] precise = new double[] {5.0 * Math.Pow(10, -324), 5.0 * Math.Pow(10, -324), 1.6 * Math.Pow(10,308), 1.7 * Math.Pow(10,308), 1.7 * Math.Pow(10,308)};
            Array.Sort(input); //sort to save yourself from the test being wrong
            Assert(2 == FindClosestMatchIndex(precise, 1.6 * Math.Pow(10,308)), "finds the straight match among large, precise numbers");
            Assert(1 == FindClosestMatchIndex(precise, 5.0 * Math.Pow(10, -324)), "finds the highest index one when duplicate exists - test #1");
            Assert(4 == FindClosestMatchIndex(precise, 1.7 * Math.Pow(10,308)),"finds the highest index one when duplicate exists - test #2");
        }
        
        public static void Assert(bool result, string message)
        {
            Console.WriteLine("Assert:{0}.  {1}", result ? "Pass":"Fail", message);
        }
        
        public static string ReverseString(string text)
        {
            if (string.IsNullOrEmpty(text)) return string.Empty;
            
            char[] textArray = text.ToCharArray();
            
            for(int i = 0, j = textArray.Length-1; i < j; i++, j--)
            {
                char temp = textArray[i];
                textArray[i] = textArray[j];
                textArray[j] = temp;
            }
            
            return new string(textArray);
        }
        
        //binary search
        public static int FindClosestMatchIndex(double[] sortedArray, double number)
        {
            
            if (sortedArray.Length == 0) return -1;
            
            int left=0;
            int right = sortedArray.Length - 1; 
            
            //find the closest range
            while ((right - left) > 1)
            {
                int mid = left + (right - left)/2;
                
                if (sortedArray[mid] > number)
                    right = mid;
                else 
                    left = mid;
            }

double diff1 = number - sortedArray[left];
            double diff2 = sortedArray[right] - number;
           
            int closestIndex;
 
            //closest is the one with the lesser difference
            if (diff1 < diff2)
                closestIndex = left;
            else
                closestIndex = right;
            
            return closestIndex;
        }
        
    }
}


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